Occupational (Contact) Dermatitis

What is it?

How is it caused in the occupational environment?

How should it be managed?

In current terminology "dermatitis" is used synonymously
with "eczema" to describe inflammatory reactions in the
skin, which are typically characterized by itching and redness but may vary from
slight thickening of the outermost layer of the skin with small fissures to extensive
redness, swelling and oozing.

Dermatitis may be entirely endogenous (constitutional) or be entirely exogenous
(contact). Exogenous dermatitis or contact dermatitis may be caused
by irritant or allergic contact reactions or both.
Dermatitis often has a multifactorial aetiology and may be aggravated by the presence
of bacterial pathogens such as staph. Aureus. When considering hand eczema it is
always worth investigating the possible role of contributory factors and assessing
the role of these. Atopic (constitutional) hand eczema is a common example of an
endogenous eczema in which exogenous factors normally compound the situation. The
other two forms of contact dermatitis are photocontact dermatitis
and contact urticaria.

An
occupational dermatitis
is one where the inflammatory reaction is caused
entirely by occupational contact factors or where such agents are partly responsible
by contributing to the reaction on compromised skin.
In most cases
occupationally related dermatitis affects the hands alone, though they may spread
onto the forearms. Occasionally, the face may be the prime site on inflammation,
as in the case of airborne contact factors.

Irritant contact dermatitis with synonym toxic, traumiterative, or housewives eczema
and non-allergic contact dermatitis is the most common variant with a point prevalence
of 1-2% in the healthy population. Localized almost exclusively to the hands it
occurs most frequently in wet work occupations such
as hairdressers, healthcare personnel, cleaners, cooks and caterers. Contactants
are detergents and surfactants, acid and alkali solutions, organic solvents, sometimes
even water. The deleterious effect of these agents is the removal of the fat emulsion
on the skin surface, a damage to the function of the epidermal skin barrier, and
removal of the water-binding substances of the outer layer. The single exposure
is usually harmless but by accumulation destructive. The clinical consequences are
dryness, scaling and fissuring, progressing to eczematous dermatitis. It occurs
where the skin is thinnest. Hence, it is often seen in the finger webs and back
of the hands rather than the palms. The most common predisposing factor for this
type of contact dermatitis is the presence of an atopic predisposition.

Allergic Contact Dermatitis

Allergic contact dermatitis is the clinical expression of contact allergy. This
type of hypersensitivity is always acquired and may develop any time during life.
The allergy-inducting agents or antigens are low-molecular so-called haptens.

The dermatitis develops at the site of skin contact with the allergen. Secondary
spread may occur. Contaminated hands may spread the allergen to previously unexposed
sites. Trivial or occult contact with an allergen may result in persistence of dermatitis.
Some allergens are essentially ubiquitous  for example formaldehyde and nickel.

It is not yet possible to determine an individuals susceptibility to developing
contact allergy. Hypersensitivity is specific to a particular molecule or to molecules
bearing allergenic sites. Although hypersensitivity may eventually be lost, the
state should be considered to last indefinitely.

Common occupational allergens

Rubber accelerating chemicals, such as thiurams and carbamates

Biocides  such as formaldehyde

Hairdressing chemicals  such as thioglycolates, phenylediamine

Epoxy resin monomers

Chromates

Plant allergens  such as sesquiterpene lactones found in Chrysanthemum.

Contact Urticaria

Contact urticaria deviates from regular contact dermatitis in the type of clinical
reaction, its time sequence, the causal agents, and the pathogenic mechanism. True,
the clinical reaction appears on the site of direct contact, usually the fingers,
but consists of small itching wheals, emerging within 10-20 minutes after contact
and rapidly disappearing. Causal agents may be latex rubber in gloves, animal proteins
or other foodstuffs, the patients often being health care personnel, as well as
chefs and workers in meat and fish industry.

Pertinent allergens are high-molecular, complete antigens, normally not absorbed
through the skin. Therefore, a precedent damage to the skin barrier e.g. discrete
irritant dermatitis, would be a prerequisite. These patients usually have an atopic
constitution.

A regular 48hour patch test will give a false negative reaction. Instead, a short
term (20min) prick test with the suspected material e.g. rubber or shrimps as is,
will provide a positive, immediate, wheal reaction. In latex cases, also specific
IgE antibodies may be demonstrated in the blood (RAST test)

Of concern is the increasing occurrence of immediate type 1 hypersensitivity to
proteins present in latex gloves. The problem is seen principally in health care
workers especially atopics working in the operating theatre or ICU. Prevalence is
about 5-10% in US and European hospitals. 12.5% of anaesthesists were sensitized
in one US study. Other workers at risk are hairdressers, 10% in one study and glove
factory workers 11% in another study.

The significance of this sensitization is that all these patients are at risk for
anaphylaxis.

Latex is the second most common cause of intraoperative anaphylaxis.

Photocontact Dermatitis

Photocontact dermatitis is the result of an interaction between a harmful substance
present in the skin and ultraviolet radiation. In other words, no dermatitis evolves
by the absorbed photosensitizer alone (e.g. if the subject stays indoors) but UV
exposure is also required. Photocontact dermatitis is therefore always localized
to light-exposed skin, viz. on face, ears, dorsal aspect of hands, and other areas
not protected by clothing. Common phototoxins are found in ubiquitous plants of
the Umbelliferae family (parsnip, fennel, carrot & celery), therefore sometimes
seen in farmers. Plants from the compositae family like chrysanthemum cause a volatile
pattern and may present as a light-aggravated or exposed site dermatitis

Management of Occupational Dermatitis

Assessment

Understanding the patients job is necessary. A job
title is not sufficient for this understanding; the question to be asked is not
"what do you do?" but "What exactly do you do and how do you do it?"
The title "engineer " can mean anything from a desk bound professional
to a lathe worker exposed to soluble coolants.

A site visit  watching the patient working –
may be necessary.

The history of the dermatitis may provide clues as to the
aetiology.

Irritant contact dermatitis may occur as an "epidemic" in a workplace
if hygiene has failed, while allergic contact dermatitis is usually sporadic.

Evaluation of contact factors  The evaluation of irritant
factors is always subjective. Evaluation of allergic contact factors is objective
and provided only by diagnostic patch tests. Properly performed,
patch tests will show the presence or absence of important allergens. Patch testing
is the only method for the objective evaluation of dermatitis. There are major pitfalls
in the use of this essential tool  proper training and experience is essential
if it is to provide valid results.

A competent assessment requires all of the above followed by recommendation on reducing
or stopping exposure to the offending agent and similar ones.

Diagnosis

The diagnosis of an occupational dermatitis should describe thoroughly the nature
of the condition, including any endogenous or aggravating factors. Delays in diagnosis
that result in continued exposure to relevant irritants or allergens can adversely
affect the prognosis.

Chemical analysis of environmental materials to determine whether
they contain a substance to which the patient is patch test positive.

Treatment of Occupational Dermatitis

Education on Prevention measures & avoidance

Primary prevention is aimed at providing appropriate information and protection.

Employer and employee should be aware of the potential risks of exposure

Education of need for good occupational hygiene

Adequate provision of suitable and effective means of reducing exposure

Awareness of limitations of personal protection devices

In a study published in Occupational Medicine in Sep. 1997 entitled " Worker
education in the primary prevention of occupational dermatoses", The paper
reports the evaluation of a skin care education program conducted on a fine chemical
manufacturing site where over 1,000 employees are located. Approximately 60% are
involved in chemical manufacture. Over a twelve-month period production staff received
training in prevention of occupational dermatoses linked to a site-wide poster initiative.
The incidence of new cases of occupational dermatoses fell from 70 cases in 1,277
employees to 27 cases in 1,277 employees, before and after the intervention respectively.

Training materials such as video and poster presentations may be effectively used
in chemical manufacturing industry as an adjunct to prevention and control of exposure
to substances hazardous to the skin. Such methods may also be used in other industries
where there are significant risks of occupational dermatitis.

Topical treatment alone may be indicated in mild cases.

Barrier / moisturizing creams

Moisturizers prevent the development of experimental irritant contact dermatitis,
and using appropriate moisturizers may also enhance the rate of healing on damaged
skin. Individuals regularly exposed to irritants should be encouraged to apply moisturizers
frequently in order to minimize dermatitis.